1. Field of the Invention
An apparatus for annunciating low-voltage in a battery supplying electricity to an auto-darkening optical filter system for a welding helmet.
2. Description of the Related Art
A conventional auto-darkening optical filter system for a welding helmet has both an optical band-pass filter that continuously blocks damaging ultraviolet and infrared radiation from reaching a welder's eyes and an auto-darkening LCD shutter that allows essentially all ambient visible light to pass but darkens in the presence of intense visible light—for example during a welding operation—to allow only a portion of the visible light to reach the welder's eyes. In this way, the welder's eyes receive an appropriate amount of visible light to see both during welding operations and otherwise. The band-pass filter and the LCD shutter are stacked one atop the other in series and both are protected by a cover glass.
Considering the LCD shutter in more detail now, an optical sensor detects light intensity proximate the cover glass. An LCD driver electrically connected to both the optical sensor and the LCD shutter applies a variable shuttering voltage to the LCD shutter to cause the LCD shutter to increase its opacity in response to increasing light intensity detected by the optical sensor. This increase in opacity may be a simple change between a transparent state and a translucent state or may be a more gradual change through multiple states of increasing translucency, for more expensive systems.
The electricity that powers such systems is generally provided by battery. It is therefore a common concern that the battery will unexpectedly deplete and be insufficient to power the system. The consequence of this situation would be that the LCD shutter could fail to darken when a welding operation commences and too much visible light could pass through the optical filter system to the welder's eyes, leading to temporary dazing or even eye irritation.
A typical solution to this problem has been to include an indicator light—often an LED—in the system, which illuminates or flashes when the battery voltage falls below a predetermined threshold and is therefore close to being insufficient to power the system. While an improvement, this arrangement has a number of disadvantages. For example, a small light can be difficult to notice in a bright welding environment. Furthermore, illuminating a light—even an energy-efficient LED—depletes the battery further.
What is needed is a way to more certainly announce battery low-voltage to a welder, which does not significantly deplete the battery further.